Any delay in resuscitating from hypoperfusion increases morbidity and mortality. Critically ill patients should be monitored continuously: to detect hypoperfusion early and quantitatively, to report the efficacy of volume and inotropic resuscitation, and to prevent reperfusion injuries. Tonometric acquisition of gastric mucosal pCO2 reduces mortality in the intensive care setting as a therapeutic adjunct. It has been proposed as a rapid and sensitive means to detect regional mesenteric hypoperfusion, which is an early homeostatic response to volume depletion and inadequate systemic blood flow. When gastric tonometry is used prospectively, it allows shock to be managed rationally: titrating resuscitative efforts to a relevant visceral endpoint. This project will demonstrate and calibrate the first microsensor suitable for remote sensing of mucosal hypercarbia in the gastrointestinal lumen. The sensor fits entirely within the distal end of a standard nasogastric or nasojejunal catheter. It provides early, real-time, low latency, quantitative detection of hypoperfusion, including burn injury, heat stroke, sepsis and hemorrhage. It can also continue to quantify, directly and in real time, the status of efforts at resuscitation from hypoperfusion. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE